Park Goo mutates into a man-fish due to side effects from an experimental drug. He receives heavy publicity and becomes a star. A conspiracy by the pharmaceutical company leads Park Goo to being possibly expelled from the world.

Gon, a Korean raised in America, is a professional hitman who is usually flawless in taking out his targets. On his latest assignment, though, Gon makes the terrible mistake of killing an innocent young girl. Overcome by regret, guilt and shame, Gon no longer wants to kill for a living, but his boss orders him to go to Korean — to eliminate the dead child's mother.

A 15-year-old circus ringmaster Wei-wei is left all alone with gorilla Ling-ling after grandfather passes away. Thanks to her grandfather's love for baseball, Ling-ling was trained to play baseball and has developed remarkable hitting skills. The materialistic sports agent Sung Chung-Su hears of this remarkable gorilla, and signs Ling-ling to play in the professional South Korean baseball league. Dreaming of success, World's first gorilla pinch hitter and his 15-year old trainer begin on their run in the Korean Baseball League.